ORIGINAL: Steve Steinbring
Good advice above!
I would like to add a couple more suggestions that I teach my students. Once advanced enough and before solo I would include practicing dead stick landings and some basic aerobatics including unusual attitudes. That way if a problem occurs he will be more likely to handle the situation.
Enjoy all the time together with your son you can time passes too quickly!
All good suggestions here, but I want to second what Steve suggested. I like to teach competent students (new pilots who have mastered basic turns and level flight) how to do basic rolls and loops. It's fun for them to practice and it helps them acclimate to having the plane being not-right-side-up all of the time and getting comfortable with various orientations.
Figure eights, square turns, slow flight, shooting approaches, take off, and landing practice will all be important steps on the way to solo flying. Mixing in a bit of fundamental aerobatics will make flying more fun and better equip the student for everything they'll want to do once they solo.